Hydraulic fracturing or “frac'ing” is a common technique that is often used to increase the rate at which fluids, such as water, gas, and oil, can be extracted from an underground reservoir. In this technique, underground fractures are generally formed by pumping fracturing fluid, which often consists of water and sand, into a well bore at a rate that is sufficient to increase the pressure downhole to a value that is greater than the fracture gradient of the surrounding rock formation. This pressure then causes the formation to crack and, thereby, allows the fracturing fluid to enter in, and to extend the cracks further into, the formation. The cracks, in turn, can act as conduits between portions of the reservoir and the well bore.
Water from the fracturing fluid often exits a gas well in one of two forms; namely as flow back water or as frac'ed well water. In this regard, the term flow back water may refer to the initial charge of water that flows from the bore and the term frac'ed well water may refer to the longer term and more contaminated version of the flow back water. In some cases, the rough balance of the two contaminated water sources is approximately 1:4, wherein about 25% of the water that exits the well is flow back water and about 75% of the contaminated water is frac'ed well water.
The handling of contaminated water from gas wells has been a problem for years. Furthermore, the magnitude of this problem may be enormous. For instance, it is estimated that a single company, in a single location, can generate as much as 70,000 barrels of contaminated water from gas wells in a day. Assuming that a barrel equals 42 gallons, such a company could produce 2,940,000 gallons of contaminated water (e.g., 70,000 barrels/day×42) from one locale each day. Along these lines, some have estimated that the total volume of water consumed and taken from the natural gas wells in the United States alone is greater than about 10 billion gallons of water per year.
While the oil and gas exploration industry has been looking for a method and technology to treat contaminated water from gas wells and to be able to return the water for reuse in the wells, such contaminated water is currently often impounded or simply injected back into deep wells.
A significant advance in the treatment of this contaminated water would result in an enormous savings of the energy required to pick up, deliver, and haul the contaminated water from each well site—processes that are currently often accomplished by trucking all the water from locale to locale. In this regard, draught affected areas may be required to move the water several hundred miles to and from the site.